INVESTIGATION OF THE EFFECT OF FEMALE LARGER GRAIN BORER, PROSTEPHANUS-TRUNCATUS (HORN) (COLEOPTERA, BOSTRICHIDAE), AND THEIR RESIDUES ON THE PRODUCTION OF AGGREGATION PHEROMONE BY MALES

The rate of production of aggregation pheromone by male larger grain b orer beetles, Prostephanus truncatus (Horn), is greatly reduced in the presence of live, conspecific female beetles. A similar effect is obs erved in the absence of live female beetles when males are placed on m aize that was previously infested with males and females, suggesting t hat it is due to some chemical residue left by the females. This was s hown to persist for at least 15 days, to be involatile and not perceiv ed by receptors on the antennae of the males. Attempts to extract the chemical(s) responsible and transfer it to a new substrate gave variab le results. Extraction of previously-infested maize with hexane, ether , dichloromethane, butanone or water under different conditions probab ly did not remove the suppression effect, but Soxhlet extraction with methanol did. However, when the resulting extract was recoated onto va rious substrates, no reduction in pheromone production by males could be demonstrated, suggesting that the methanol is extracting and/or des troying the chemical(s) responsible. Crown Copyright (C) 1996 Publishe d by Elsevier Science Ltd